1. Field of the Invention
The present invention relates to Benes networks having an add-drop function, and more particularly to add-drop Benes networks capable of minimizing network complexity by adding a minimum number of additional elements to the existing Benes networks, which are a representative example of rearrangeably nonblocking networks and performing an add-drop function using a simple algorithm.
2. Description of the Related Art
Research into a space-division switching technology has been widely conducted not only in a network field and but also in the natural world. In a space-division switching network, an input-output pair is connected through a physical path, and different inputs and outputs are connected through different physical paths. The space-division switching network is divided into a partial connection network, a full connection network, a rearrangeably nonblocking network and a strictly nonblocking switching network according to input-output connection performance.
In particular, the rearrangeably nonblocking network is characterized in that, when a new input-output pair is connected, a predetermined switching network connection state is changed, and network elements, such as 2×2 switches, less in number than the number of network elements of the strictly nonblocking network are necessary.
The Benes networks are a representative example of rearrangeably nonblocking networks, and research into a network architecture and a driving algorithm thereof has been actively conducted.
FIG. 1 is a diagram showing the configuration of the existing 8×8 Benes networks. The Benes networks are a representative example of the rearrangeably nonblocking switching networks, and are characterized in that various physical paths from one input port to one output port are formed and an internal path of the existing switching network is rearranged when a physical connection of a new idle input-output pair within the network is determined. The Benes networks are composed of a combination of 2×2 switches. When the number of input/output ports is N, the whole networks are composed of 2 log2 N−1 stages and each stage is composed of N/2 2×2 switches. That is, N×N Benes networks having N inputs/outputs are composed of a total of
      N    (                            log          2                ⁢        N            -              1        2              )    ⁢          ⁢  2  ×  2switches.
In a looping algorithm for driving the Benes networks, there is a limitation that different input ports based on a time slot always have different output ports as destinations. In addition, an add-drop function is required for expandability, maintenance and repair of the networks.
Add-drop Benes networks which were suggested in the related art in order to solve such problems are shown in FIG. 2.
The architecture of the add-drop Benes networks of the related art shown in FIG. 2 includes an input stage 110 having eight input ports, an output stage 120 having eight output ports, an add input stage 130 having eight add ports, a drop output stage 140 having eight drop ports, first and second input connection stages 151 and 152 composed of four 2×2 switches to connect the input stage 110 and the add input stage 130, first and second intermediate connection stages 171 and 172 for connecting the outputs of the first and second input connection stages 151 and 152, and first and second output connection stages 161 and 162 for selectively connecting the outputs of the first and second intermediate connection stages 171 and 172 to the output stage 120 and the drop output stage 140.
In the add-drop Benes networks of the related art having such an architecture, if N×N add-drop Benes networks are implemented using 2N×2N Benes networks, N input ports of the input/output ports of the 2N×2N Benes networks are used as the add ports and N output ports thereof are used as the drop ports so as to implement the N×N add-drop Benes networks having an add-drop function. Accordingly, many switches, that is,
  2  ⁢      N    (                            log          2                ⁢        2        ⁢        N            -              1        2              )    ⁢          ⁢  2  ×  2switches are required.